In prior art vehicles or conveyances, such as snowmobiles or the so called jet skies which are used on water, sometimes have retaining or holding devices. For example, in U.S. Pat. No. 3,730,552 to Clark an anchoring device for a snowmobile on a trailer is shown which an apertured bar on the snowmobile is inserted into a selected slot on a retaining plate mounted on a trailer. U.S. Pat. No. 3,672,523 to Albert is directed to a snowmobile trailer which shows a device for holding a snowmobile on a trailer in which an assembly is resiliently urged toward an elevated position, so that it hooks under the snowmobile when it is pulled over the assembly. However, even though these prior art devices disclose holding or retaining means, there is no locking arrangement shown which prevents the holding or retaining device from being removed and the conveyance stolen from the trailer that it rests on.